Multiparametric flow cytometry has proven to be an indispensable tool for numerous areas of biological and medical research at the University of Chicago. The ability to identify and enumerate individual living cells in a precise and rapid fashion has allowed for the characterization of rare cell types from any number of tissues and organs. The ability to detect such events is particularly crucial for the study of cancer and immune-mediated diseases. Previously, multiparametric flow cytometers have been able to identify many such cell types;however the limits of fluorescence detection have been reached on many commercial instruments. The necessity to resolve cell types with very low antigen expression has become evident in the area of stem cell research and hematopoiesis. Therefore, it is evident that instrumentation that will be able to detect multiple parameters simultaneously at high through-put rates, and also resolve these dimly fluorescent cell subtypes, is necessary for the continued advancement of the research at the University of Chicago. A new, high sensitivity, 4-laser, 14-parameter BD LSRII will allow for these detection criterion, and also alleviate some of the capacity issues currently experienced by the user base. A 15% increase in usage of the current facility's LSRII and the loss of the Cyan-ADP has forced the facility to begin leasing the requested LSRII. As such this proposal has been revised to request funding to buyout the leased instrument so that the major investigators may continue to perform their studies. Twelve major users with as many NIH funded projects focusing on a wide variety of biomedical science including hematopoiesis, asthma, host defense, lung injury, transplantation, autoimmune diseases as well as basic cancer and immunology research, will depend on this instrumentation. The efficiency of the usage of this instrument will be aided by its placement in the University of Chicago Flow Cytometry Core Facility on campus. By placing this instrument in the already established core facility on campus (serving >80 PI's), the faculty will be able to exploit the expert knowledge of the facility directors and staff in its operation and usage. Further, in the core facility equal access is provided to all University Investigators. Thus, this instrument will greatly benefit the University of Chicago by easing current capacity issues and providing state-of-the-art technology, allowing our investigators to remain at the forefront of their research. PUBLIC HEALTH RELEVANCE: Twelve NIH funded projects focusing on biomedical research areas such as hematopoiesis, asthma, host defense, lung injury, transplantation, autoimmune diseases, mechanisms of cancer and immunology will rely heavily on the requested instrumentation. State-of-the-art technologies employed on the requested instrument will help unveil the information necessary to answer these important questions.